It showed one of the most impressive increases in helmet use following adoption of a law to date: from 4 percent to 47 percent (8).
Although observational studies are considered preferable to telephone surveys, they are relatively resource-intensive and thus have been applied only to local or county jurisdictions.
Florida is an excellent site at which to study the effectiveness of a state law mandating use of bicycle helmets.
Because populations of riders from different geographic areas are likely to differ in their exposure to traffic, trip duration, and pattern of helmet use, developing a probability sample based on exposure to bicycle-riding is challenging, if not impossible.
In counties where the state law was in place, 16,907 (79%) of 21,313 riders observed wore a helmet, compared with only 148 (33%) of 450 riders in counties where no such law was in place (crude prevalence ratio = 2.4, 95% confidence interval: 2.1, 2.8).
Helmet use by children of all racial groups exceeded 60% under the law.
Local findings may not be generalizable to larger populations, because of the relative socioeconomic homogeneity of a single county.
Statewide surveys would be more representative of the entire national population.